.\"	$OpenBSD: umbg.4,v 1.4 2013/07/16 16:05:49 schwarze Exp $
.\"
.\" Copyright (c) 2007 Marc Balmer <mbalmer@openbsd.org>
.\"
.\" Permission to use, copy, modify, and distribute this software for any
.\" purpose with or without fee is hereby granted, provided that the above
.\" copyright notice and this permission notice appear in all copies.
.\"
.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
.\"
.Dd $Mdocdate: July 16 2013 $
.Dt UMBG 4
.Os
.Sh NAME
.Nm umbg
.Nd Meinberg Funkuhren USB5131 timedelta sensor
.Sh SYNOPSIS
.Cd "umbg* at uhub?"
.Sh DESCRIPTION
The
.Nm
driver provides support for the Meinberg Funkuhren USB5131, a time signal
station receiver for the German DCF77 station.
.Nm
implements a timedelta sensor and the delta (in nanoseconds) between the
received time information and the local time can be accessed through the
.Xr sysctl 8
interface.
.Pp
The quality of the timedelta is reported as the sensor status:
.Bl -tag -width "CRITICALXX" -offset indent
.It UNKNOWN
No valid time information has been received yet.
.It OK
The time information is valid and the timedelta is safe to use for
applications like
.Xr ntpd 8 .
.It WARN
The time information is still valid, but no new time information has been
decoded for at least twelve hours due to a reception or parity error.
The timedelta should be used with care.
.It CRITICAL
No valid time information has been received for more than twelve hours since
the sensor state degraded from OK to WARN.
This is an indication that hardware should be checked
to see if it is still functional.
.El
.Pp
A second sensor provides the relative signal quality as a percentage.
The status of this sensor is used to report the status of the device itself:
.Bl -tag -width "CRITICALXX" -offset indent
.It OK
The clock is synchronized.
.It WARN
The device's clock is free running on the local oscillator.
This is not an error and can happen due to the nature of the signal
transmission using longwave radio.
.It CRITICAL
Hardware failure, e.g. communication with the device failed.
.El
.Sh SEE ALSO
.Xr intro 4 ,
.Xr usb 4 ,
.Xr ntpd 8 ,
.Xr sysctl 8
.Sh HISTORY
The
.Nm
driver first appeared in
.Ox 4.3 .
.Sh AUTHORS
The
.Nm
driver was written by
.An Marc Balmer Aq Mt mbalmer@openbsd.org .
